5-tert-butyl-metaxylene (5tBuMX) is a necessary feedstock in the production of tert-butyl-isophthalic acid and other intermediates in the production of industrial chemicals. 5tBuMX is generally produced by the alkylation of metaxylene with isobutylene using a catalyst.
Catalysts commonly used in the production of 5tBuMX are aluminum halides, strong acids and hydrogen fluoride. U.S. Pat. No. 3,379,787 to Amir discloses the alkylation of C8 aromatic hydrocarbon with diisobutylene or trilsobutylene and using anhydrous aluminum chloride liquid as a catalyst. U.S. Pat. No. 4,551,573 to Cobb discloses addition of elemental iodine to improve alkylation of aromatic compounds using an aluminum halide catalyst. U.S. Pat. No. 3,284,523 to Beck et al. discloses a method for the production of 5tBuMX by alkylation of metaxylene using a sulfuric acid catalyst. Great Britain Patent No. 1,227,419 to Japan Gas Co. discloses the use of a hydrogen fluoride catalyst.
Use of aluminum halide catalysts results in low yield. Strong acid catalysts provide poor selectivity for the 5tBuMX Isomer, and a significant amount of 4tBuMX is created which must be separated from the 5tBuMX isomer. The toxicity of hydrogen fluoride makes it very difficult to handle. Currently, catalysts are used In a liquid or gas phase. Separating the catalyst from the reaction products is difficult. Additionally, catalysts currently used in the art result in environmentally unfriendly waste products. There is a need for a method to produce 5tBuMX with sufficient yield and high selectivity while using a catalyst that can be easily separated from the reaction products and results in less waste material and where the waste material is environmentally benign.
Ghosh discloses use of a solid acid montmorillonite clay catalyst in separation of metaxylene and paraxylene. Separation Through Reactions, Dept. of Chemical Technology, University of Bombay, September 1991. Japanese Patent No. 03024021 to Fujita, et al. discloses use of an active clay catalyst for production of 5tBuMX by the alkylation of metaxylene with isobutylene. Use of an active clay catalyst results in higher conversion of isobutylene but less than 50% conversion of metaxylene. Active clay catalyst also shows high selectivity for 5tBuMX, and can be separated from reaction products by known methods such as filtration. Unfortunately, use of clay catalyst in accordance with the disclosure of Fujita et al. results in unacceptably rapid deactivation of the clay catalyst. Rapid deactivation of clay catalyst and low metaxylene conversion result in excessive waste, much of which is environmentally harmful. Additionally, large scale production of 5tBuMX in accordance with the disclosure of Fujita et al. would consume excessive amounts of clay catalyst and metaxylene thereby making its large-scale use unfeasible. There is a need for a process for the production of 5tBuMX using a solid catalyst that maximizes catalyst life, maximizes isobutylene conversion, provides high selectivity for the 5tBuMX isomer, and minimizes waste product.